Visual Field Defects
Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management
Definition
Visual field defects refer to areas of lost or reduced vision within the normal visual field, resulting from pathology affecting the retina, optic nerve, optic chiasm, or visual pathways in the brain.
Aetiology
- Retinal causes: retinal detachment, diabetic retinopathy, age-related macular degeneration.
- Optic nerve pathology: glaucoma, optic neuritis, ischaemic optic neuropathy.
- Optic chiasm lesions: pituitary adenomas, craniopharyngiomas.
- Post-chiasmal pathology: stroke, occipital lobe lesions, traumatic brain injury.
Pathophysiology
- Damage to the retina results in focal visual loss corresponding to the affected area.
- Optic nerve involvement leads to monocular visual field loss.
- Chiasmal lesions cause bitemporal hemianopia due to disruption of crossing nasal fibres.
- Post-chiasmal lesions result in homonymous hemianopia, with defects affecting the same side of the visual field in both eyes.
Risk Factors
- Hypertension and cardiovascular disease.
- Diabetes mellitus.
- Glaucoma.
- Brain tumours or history of head trauma.
- Multiple sclerosis.
Signs and Symptoms
- Monocular vision loss: suggests optic nerve involvement.
- Bitemporal hemianopia: associated with chiasmal lesions.
- Homonymous hemianopia: indicative of post-chiasmal pathology.
- Scotomas: central or peripheral blind spots.
- Transient visual loss: seen in amaurosis fugax or transient ischaemic attacks.
Investigations
- Visual field testing (perimetry): assesses extent and pattern of visual loss.
- Fundoscopy: evaluates for retinal or optic nerve pathology.
- OCT (optical coherence tomography): assesses retinal nerve fibre layer.
- Brain MRI: detects structural lesions affecting the visual pathway.
- Blood tests: ESR, CRP if giant cell arteritis is suspected.
Management
1. Treat Underlying Cause:
- Glaucoma management with intraocular pressure-lowering agents.
- Urgent steroids in suspected giant cell arteritis.
- Stroke management including antiplatelet therapy if vascular pathology is identified.
2. Supportive Care:
- Low vision aids and occupational therapy for patients with persistent defects.
3. Referral:
- Ophthalmology: for all suspected cases requiring assessment.
- Neurology: if neurological involvement is suspected.
- Endocrinology: for pituitary lesions affecting the optic chiasm.